A complete set of golf club irons typically includes a set of twelve irons numbered from 2 (long) through 9 (short), a pitching wedge (PW), a gap wedge (GW) and a sand wedge (SW). A 1-iron is also sometimes included in the set, although the average golf club set does not include a 1-iron due to difficulty in using the club. Each iron typically comprises a head including a hosel and a shaft which is attached to the head by fitting the shaft into a bore of the hosel. The hosel is integrally formed as part of the head. The head also includes a heel, a bottom sole, a toe, a planar striking face, and a back side.
The typical twelve irons of a golf club set have varying degrees of loft angle. The loft angle of an iron is the angle between a vertical plane, which includes the shaft, and the plane of the striking face of the iron. The loft angle effects how much loft is imparted to the ball when it is struck by the tilted, striking face.
Longer-hitting irons (i.e., #2, #3, #4) have progressively longer golf club shafts than the shorter-hitting irons (i.e., #5, #6, #7, #8, #9, PW, SW). Typically, the length of the golf club shaft progressively increases in length from PW through the 2-iron. Further, it is a typical design criteria that each golf club within a set have the same substantially identical swing weight. As the volume of shaft is different for each club due to varying length, the mass of the club head is varied inversely to the length of the shaft such that a substantially constant swing weight is achieved for each club within a complete set. Accordingly, typically the PW head is heaviest and the 2-iron head is lightest within a given set 2-iron through PW.
The amount of spin imparted to a golf ball is affected by a combination of the design of the club head and the impact the golfer makes with the ball. Professional golfers, because of their ability, typically can modify their swing and impact selectively, particularly with the higher numbered short irons, to affect the degree of backspin a ball will have when hitting the green. Degree of backspin on the ball when it hits in part determines where the ball will stop. At some point, the back spin can become so great that the ball draws back from where it hits the green.
Relative to head design, probably the most significant feature impacting the degree of backspin that can be put on a ball relates to the groove design in the face of a golf club iron head. The U.S.G.A. has rules which impact the configuration of groove design for golf clubs. The existing U.S.G.A. rules read:                A series of straight grooves with diverging sides and a symmetrical cross-section may be used (see FIG. IX). The width and cross-section must be consistent across the face of the club and along the length of the grooves. Any rounding of groove edges shall be in the form of a radius which does not exceed 0.020 inches (0.5 mm). The width of the grooves shall not exceed 0.035 inches (0.9 mm), using the 30 degree method of measurement on file with the United States Golf Association. The distance between edges of adjacent grooves must not be less than three times the width of a groove, and not less than 0.075 inches (1.9 mm). The depth of a groove must not exceed 0.020 inches (0.5 mm).        
It would be most desirable to develop improved groove designs which fall within the scope of the existing or future U.S.G.A. rules.